Gj. Mckay et Lr. Cooke, A PCR-BASED METHOD TO CHARACTERIZE AND IDENTIFY BENZIMIDAZOLE RESISTANCE IN HELMINTHOSPORIUM-SOLANI, FEMS microbiology letters, 152(2), 1997, pp. 371-378
Control of Helminthosporium solani, the cause of silver scurf in potat
o tubers, has been impaired by selection of benzimidazole-resistant st
rains as a result of repeated use of the fungicide thiabendazole. Iden
tification of thiabendazole-resistant strains of H. solani by conventi
onal techniques takes several weeks. Primers designed from conserved r
egions of the fungal beta-tubulin gene were used to PCR amplify and se
quence a portion of the gene. A point mutation was detected at codon 1
98 in thiabendazole-resistant isolates causing a change in the amino a
cid sequence from glutamic acid to alanine or glutamine. Species-speci
fic PCR primers designed to amplify this region were used in conjuncti
on with a restriction endonuclease to cause cleavage in sensitive isol
ates only and thus provide a rapid diagnostic test to differentiate fi
eld isolates.